Moment Capacity Research Articles

A numerical study on the seismic retrofit of Haitian reinforced concrete building frames

Many countries with moderate and high seismic risk have upgraded their building design standards and have developed techniques to strengthen their seismically deficient buildings. However, very limited research has been conducted on the seismic evaluation and retrofit of Haiti’s existing buildings. In an effort toward filling this gap, after reviewing the reinforced concrete (RC) building construction practices in Haiti, this article numerically evaluates the seismic performances of four different non-ductile RC building frames typical of Haiti and five different techniques to retrofit those. Specifically, the selected RC building frames are of one to three stories and of residential and non-residential functions. The examined retrofit techniques include using RC shear walls, using steel braces, using buckling-restrained braces (BRBs), using prestressed high-strength steel cables, and RC jacketing. To examine the damage of the columns and the beam-to-column joints of the original frame archetypes, their detailed three-dimensional finite element models are initially developed and analyzed via the software LS-DYNA. Subsequently, each frame is retrofitted through three of the above-mentioned techniques. A suite of 11 ground motions is selected and scaled to evaluate the effectiveness of the retrofits by performing time-history analysis on calibrated models on OpenSees. The analysis indicated that these techniques can efficiently retrofit the prototypes of Haitian structures. All the retrofits significantly reduce the interstory drift demand, and the RC jacket significantly increases the moment and shear capacity of the columns.

Experimental and numerical analysis of self-compacting geopolymer concrete composite slab

Composite slab systems have earned high regard in the building industry as a fast-track construction and an economical approach. Geopolymer concrete has been recognised as an environmentally friendly material that produces lower CO2 emissions than conventional cement-based concrete. This paper compares the structural and shear bond performance of a composite slab incorporating self-compacting geopolymer concrete (SCGC) to that of a normal concrete (NC) composite slab. This research also focuses on the structural performance of SCGC composite slab reinforced with a 2% basalt fibres (BFs) dosage. BFs have been acknowledged for their sustainable feature and outstanding mechanical properties, making them a feasible choice compared to their counterparts. This study examined full-scale composite slabs made of NC, SCGC and self-compacted geopolymer concrete reinforced with BFs (SCGCB), with a targeted compressive strength of 32MPa, subjected to a four-point flexural test. Composite slabs were tested with two different shear spans of 600mm (long) and 300mm (short). The performance of composite slabs was assessed in terms of failure modes, load-deflection response, a flexural strain developed at concrete and profiled sheet surfaces, load-slip response, moment capacity, energy-based ductility of a composite slab, and shear bond resistance. SCGC showed an average 7.96% lower shear bond capacity than the NC composite slab. SCGCB composite slabs exhibited an overall noticeable improvement in load-carrying capacity, strain capacity, ductility and shear bond resistance compared to SCGC composite slabs. A nonlinear finite element model was developed to predict the shear bond capacity of SCGC and SCGCB composite slabs. The developed model was validated against the experimental results, showing good agreement with a variance of less than 10%

Experimental Investigation of Embedment Depth Effects on the Rocking Behavior of Foundations

Shallow foundations supporting high-rise structures are often subjected to extreme lateral loading from wind and seismic activities. Nonlinear soil–foundation system behaviors, such as foundation uplift or bearing capacity mobilization (i.e., rocking behavior), can act as energy dissipation mechanisms, potentially reducing structural demands. However, such merits may be achieved at the expense of large residual deformations and settlements, which are influenced by various factors. One key factor which is highly influential on soil deformation mechanisms during rocking is the foundation embedment depth. This aspect of rocking foundations is investigated in this study under varying subgrade densities and initial vertical factors of safety (FSv), using the PIV technique and appropriate instrumentation. A series of reduced-scale slow cyclic tests were performed using a single-degree-of-freedom (SDOF) structure model. This study first examines the deformation mechanisms of strip foundations with depth-to-width (D/B) ratios of 0, 0.25, and 1, and then explores the effects of embedment depth on the performance of square foundations, evaluating moment capacity, settlement, recentering capability, rotational stiffness, and damping characteristics. The results demonstrate that the predominant deformation mechanism of the soil mass transitions from a wedge mechanism in surface foundations to a scoop mechanism in embedded foundations. Increasing the embedment depth enhances recentering capabilities, reduces damping, decreases settlement, increases rotational stiffness, and improves the moment capacity of the foundations. This comprehensive exploration of foundation performance and soil deformation mechanisms, considering varying embedment depths, FSv values, and soil relative densities, offers insights for optimizing the performance of rocking foundations under lateral loading conditions.

Strengthening of pre-loaded RC beams using sustainable ambient-cured FA/GGBS geopolymer mortar

AbstractThis study investigates the effect of using ambient-cured geopolymer mortar (GPM) made of fly ash (FA) and ground-granulated blast furnace slag (GGBS) as a sustainable strengthening material on the flexural behaviour of pre-loaded reinforced concrete (RC) beams. Ten RC beams were prepared, and then eight of them were loaded at different levels and strengthened with different depths using FA/GGBS-based GPM. The investigated parameters in this study include the effect of pre-loading level and strengthening depth on the ultimate moment capacity, midspan deflection, initial stiffness, toughness, and mode of failure. The obtained results of this study showed that strengthening 50% pre-loaded RC beams using GPM at a depth of 25 mm contributed to improving the moment capacity by about 10%. It was also found that using FA/GGBS-based GPM to strengthen RC beams with a thick layer of GPM affected the flexural behaviour of the strengthened beams negatively. Finally, an analytical model provided by the ACI code was implemented to predict the ultimate moment capacity and instantaneous deflection of the GPM-strengthened RC beams.

Confined compressive stress–strain model for rectangular geopolymer reinforced concrete members

AbstractIn response to the urgent global challenge of mitigating climate change, sustainable materials have become a focal point across industries, including construction. The construction sector, recognizing its significant contribution to carbon dioxide emissions, has embarked on a relentless pursuit of eco‐friendly practices. Efforts to explore alternatives to cement, notorious for its substantial carbon footprint, have attracted considerable attention. Within this context, the present study delves into an in‐depth analysis of the stress–strain properties exhibited by geopolymer concrete (GC) column members. The primary objective is to develop a comprehensive material model of geopolymer concrete to estimate the flexural capacities of column members. To this end, inspired by the confinement model by Kent and Park, a stress–strain model incorporating the effect of confinement is proposed to accurately estimate the moment capacity of GC columns. The performance of the proposed formulation is checked using 41 different test results obtained from previous research on GC columns. Evaluations on the moment capacity estimations of the proposed model show that the results are promising in reflecting the behavior of geopolymer columns. In addition, moment–curvature curves from six recent experiments are also compared with the moment–curvature curve estimations using the proposed stress–strain model. Results show very close estimations, proving the ability of the model to be a good candidate for the performance‐based design calculations. Besides, the performance of the existing formulations from four prominent international codes (ACI318, BS8110‐97, TS500, and AASHTO) are compared with the proposed model. Notably, the flexural capacity calculated using the code formulations exhibited significant deviations from the experimental results. In contrast, the proposed model demonstrates a strong correlation with the experimental data, substantiating its effectiveness in accurately predicting the flexural capacities of GC columns.

The Behavior of Elbow Elements at Pure Bending Applications Compared to Beam and Shell Element Models

Abstract This paper studies the response of ELBOW31 and ELBOW31B element types under pure bending conditions, using shell and beam element models for benchmarking. Various model lengths are evaluated, showing that a model length of six pipe diameters exhibits a hardening effect when total strain exceeds 3.5%, though a strain up to 1% is deemed sufficient for pipeline design. The study examines the effects of ovality modes and boundary conditions such as NOWARP and NOOVAL on the bending response. ELBOW31 with one or two ovality modes yields accurate results, while additional ovality modes or zero ovality mode can lead to overprediction of the elastic bending moment capacity. The introduction of the NOWARP condition enhances the accuracy of the ELBOW31 model, while the NOOVAL condition alone produces unrealistic results. The simplified ELBOW31B model shows good agreement with the ELBOW31-NOWARP model but similarly overpredicts the bending moment when zero ovality mode is used. The study also finds that Poisson's ratio and model length have no significant impact on the bending response when no restrictions are applied. Additional analyses, as presented in Appendices A and B, highlight the importance of D/t ratios in pipeline performance. A D/t ratio of 20 offers a stiffer response with reduced ovalization, while a D/t ratio of 50 results in greater flexibility and increased ovalization. These findings provide valuable insights for the selection of element types, boundary conditions, and D/t ratios in robust pipeline design.

Numerical study of the effect of circular openings in the upper surface of rectangular hollow flange steel beams on the sectional moment capacity

Rectangular Hollow Flange (RHF) steel beams may have openings drilled in their top surface to pass some plumbing and electrical wiring inside the RHF cavity. These openings affect the behavior of these steel beams and may reduce their resistance to bending moment. To investigate this effect, Finite Element Modeling (FEM) was used to simulate RHF steel beams with and without flange openings with several variables in geometric dimensions. The FEM results were examined using 8 experimental test specimens of RHF steel beams obtained from previous studies without flange openings. The results showed high accuracy in modeling these RHF steel beams in structural behavior and ultimate bending moment capacity. Current design codes were applied to predict the capacity of these RHF steel beams without flange openings, both from FEM results and experimental tests. The prediction values were always less than the ultimate capacity of RHF steel beams without flange openings. After verifying the results, 98 RHF steel beams with different flange opening diameters were modeled. The reduction ratios in ultimate capacity in steel beams with hollow flange openings are directly proportional to the opening diameter, hollow flange height, and steel yield stress, while they are inversely proportional to the thickness and width of the hollow flange and the steel beam web height. The reduction ratios in the ultimate capacity for RHF steel beams with flange openings are small in the compact category, and these ratios increase with the non-compact and slender categories.

Seismic performance of CFDST column to steel beam welded-bolted joint with slab

To study the impact of RC slab on the seismic performance of CFDST column to steel beam welded-bolted joint, two CFDST column to steel beam welded-bolted joints with RC slab and two without RC slab were designed and fabricated. Low-cycle reciprocating load tests were conducted to analyze the effects of different configurations and the failure modes, hysteresis curves, skeleton curves, ductility, energy dissipation capacity, beam-end strain of the joint. The results showed that the hysteresis curves of all joints were relatively full and exhibited no pinching phenomenon. All joints experienced ductile failure, with failure modes characterized by tensile fracture at the connection between the steel beam upper flange and the upper ring plate, tensile tearing at the transition sections of the upper ring plate, wavy plastic deformation of the upper flange under compression, or crushing of the RC slab. The RC slab effectively improved the moment capacity, ductility, and energy dissipation capacity of the specimens, and also delayed the stiffness and strength degradation. The moment capacity, ductility, initial stiffness, and energy dissipation capacity of the specimens were reduced by decreasing the number of bolts in the lower ring plate. The nonlinear finite element method (FEM) models of the composite joints were established using Abaqus, and the failure modes and moment capacity obtained from the models were in good agreement with the experimental results. Based on the validated FEM models, some design parameters of the joints were explored.

Investigation on probability model of bending moment-rotation relationship for bolt-ball joints

As a representative semi-rigid connection, accurately predicting the mechanical properties of bolt-ball joints is of significant importance for structural design. The impact of axial load should be considered in the derivation for the initial stiffness of bolt-ball joints and its bending moment capacity. Because of the variability of geometric dimension and stochastic mechanical property of material, there is a degree of randomness in the actual mechanical behavior of the joints. In order to quantify the randomness in the bending performance, theoretical study was first carried out for the initial stiffness and bending moment capacity of the joint considering effects of axial load, which can accurately predict the bending mechanical performance of bolt-ball joints. Furthermore, the Monte Carlo method was utilized to study the impact of uncertainties in material mechanical properties, joint geometric dimensions, and assembly tightness on the bending performance. Utilizing the Latin Hypercube Sampling (LHS) methodology, a dataset comprising 10,000 samples were systematically extracted for each of the five distinct sizes of bolt-ball joints, and their stochastic responses for initial stiffness and bending moment capacity were obtained using Matlab software. Moreover, the additional variability in initial stiffness and bending moment capacity due to model uncertainty was considered and quantified. By combining the randomness of initial stiffness and bending moment capacity with the additional variability, a three-parameter power function model with random parameters was developed to establish a probabilistic model for the bending moment-rotation relationship of bolt-ball joints.

Experimental and Numerical Investigation of Buckling Behaviour in Q690 High-Strength Steel Tubes Under Combined Axial Compression and Bending Loads

This paper investigates the buckling behavior of Q690 high-strength steel tubes under combined axial compression and bending loads through experimental testing and finite element analysis (FEA). A total of 27 full-scale specimens with varying slenderness ratios (λ) and diameter-to-thickness (D/t) ratios were tested to evaluate their load-bearing capacity, deformation characteristics, and failure modes. The experimental setup replicated real-world conditions, with constant axial loads applied alongside incremental bending moments until failure occurred. FEA models, developed using ABAQUS, incorporated geometric imperfections and material nonlinearities to simulate realistic structural behavior and predict critical buckling moments. The comparison between experimental and numerical results showed strong agreement, with deviations ranging from 5.6% to 7.9%, confirming the reliability of the simulations. The findings indicate that tubes with higher D/t ratios are more sensitive to imperfections, experiencing significant reductions in post-buckling moment capacity, while those with lower D/t ratios demonstrated greater resistance to buckling and maintained higher structural integrity. The transition between global and local buckling modes was effectively captured by both experimental and numerical approaches, validating the robustness of the models. This study emphasizes the importance of accounting for geometric imperfections and residual stresses in design practices to ensure the safety and reliability of high-strength steel structures under combined loading conditions. Additionally, the results underscore the effectiveness of advanced FEA tools in predicting structural behavior, providing valuable insights for improving design codes and practices. Future research is recommended to explore dynamic loading scenarios, such as wind or seismic effects, to further enhance the applicability of Q690 steel tubes in critical infrastructure projects.

Reliability Analysis for Dynamic Behaviour, Stiffness, and Strength of Existing Steel Truss Bridge BH77

Railway bridges are old, especially on the Sumatra island and according to earthquake map on 2017 version show an increased risk, it is necessary to analyze the reliability of dynamic behaviour to extend the bridge life and damage can be detected early. The bridge reliability was assessed in terms of natural frequency, deflection, and internal force . The study was conducted on the BH77 Railway Bridge in Tegineneng-Lampung, a through truss type. Reliability analysis with a non-deterministic approach, using the probability concept, variability used is the dimensions of steel profiles based on fabrication drawings and field measurements. The research uses secondary data, one of which is measurement of the circumference of the steel cross section, that influenced by the paint layer, where the paint thickness sample to correct and obtain the actual dimensions. Dynamic behaviour analysis, consisting of modal analysis, Fast Fourier Transform, time history, and First Order Reliabilty Method. The analysis results showed the effect of steel dimension correction compared to the fabrication drawings did not have a significant effect on the changes in the values of natural frequencies, mode shapes, deflections, and internal forces. The reliability of the dynamic behaviour obtained was 99% at all reviews. Which indicates that the bridge is safe against potential resonance, the bridge stiffness is still high, and the axial+moment capacity is still sufficient against static & earthquake loads, as well as good bridge maintenance. The largest deflection point as a reference for placing strain and vibration gauges on structural health monitoring systems.

Bending Test of Rectangular High-Strength Steel Fiber-Reinforced Concrete-Filled Steel Tubular Beams with Stiffeners

To better understand the bending performance of rectangular high-strength steel fiber-reinforced concrete (HSFRC)-filled steel tubular (HSFRCFST) beams with internal stiffeners, ten beams were subjected to a four-point bending test. The primary considerations were the strength grade of the HSFRC, the steel fiber content, the internal stiffener type, and the circular hole spacing of the perfobond stiffener. The moment–curvature and flexural load–deflection curves were calculated. The mode of failure and the distribution of cracks of the infill HSFRC were observed. The presence of steel fibers greatly improved the bending stiffness and moment capacity of HSFRCFST beams, with the optimal effect happening at a steel fiber content of 1.2% by volume, according to the experimental findings. The type of stiffener influenced the failure modes of the exterior rectangular steel tube, which were unaffected by the compressive strength of the infill HSFRC. On the tension surface of HSFRCFST beams, the crack spacing of the infill HSFRC was virtually identical to the circular hole spacing of perfobond stiffeners. When the circular hole spacing was between two and three times the diameter, the perfobond stiffener worked best with the infill HSFRC. The test beams’ ductility index was greater than 1.16, indicating good ductility. The test beams’ rotational capacities ranged from 6.26 to 13.20, which were greater than 3.0 and met the requirements of the specification. The experimental results demonstrate that a reasonable design of the steel fiber content and the spacing between circular holes of perfobond stiffeners can significantly improve the bending resistance of rectangular HSFRCFST beams. This provides relevant parameter design suggestions for improving the ductility and bearing capacity of steel fiber-reinforced concrete beams in practical construction. Finally, a design formula for the moment capacity of rectangular HSFRCFST beams with stiffeners is presented, which corresponds well with the experimental findings.

Bending, torsion and flexural-torsional buckling of back-to-back cold-formed steel channels

The bending moment resistance of cold-formed steel channels can be improved by combining two channel sections with a pair of screw fasteners in the webs spaced intermediately along the member. By combining the two channels in this way, the moment capacity of the beam can be increased beyond the capacity of two single channels. Another advantage of this type of section is the coincidence of the centroid and shear centre which reduces the effects of stresses due to eccentric load and torsion. Most research on back-to-back channels in bending has focused on local and distortional buckling while data on flexural-torsional buckling is scarce. The flexural-torsional buckling resistance of a beam depends on various section properties which include the minor axis second moment of area, and the torsion and warping constants of the section. Although the flexural-torsional buckling moment can be easily determined for a single channel section because these section properties are relatively straightforward to calculate, the calculation of the flexural-torsional buckling moment for back-to-back channels with intermediately spaced screw fasteners is much more complicated due to the discontinuity of the cross-section along the length of the beam. In this paper, the shear stiffness of the screw fasteners connecting the channels is obtained from test results. The shear stiffness is then used to model the screw fasteners in a finite element analysis to analyse a beam composed of back-to-back channels under bending and torsion. The results are compared with two single channel sections and with back-to-back channels assuming full composite action. The effect of different screw fastener spacings is also investigated. Simple relationships between the bending and torsion section properties for single channels and back-to-back channels are presented. Suggestions for the design of back-to-back channels in bending are also proposed.

Structural Behavior of Full-Depth Deck Panels Having Developed Closure Strips Reinforced with GFRP Bars and Filled with UHPFRC

The adoption of prefabricated elements and systems (PBES) in accelerating bridge construction (ABC) and rapidly replacing aging infrastructure has attracted considerable attention from bridge authorities. These prefabricated components facilitate quick assembly, which diminishes the environmental footprint at the construction site, alleviates delays and lane closures, reduces disruption for the traveling public, and ultimately conserves both time and taxpayer resources. The current paper explores the structural behavior of a reinforced concrete (RC) precast full-depth deck panel (FDDP) having 175 mm projected glass-fiber-reinforced polymer (GFRP) bars embedded into a 200 mm wide closure strip filled with ultra-high-performance fiber-reinforced concrete (UHPFRC). Three joint details for moment-resisting connections (MRCs), named the angle joint, C-joint, and zigzag joint, were constructed and loaded to collapse. The controlled slabs and mid-span-connected precast FDDPs were statically loaded to collapse under concentric or eccentric wheel loading. The moment capacity of the controlled slab reinforced with GFRP bars compared with the concrete slab reinforced with steel reinforcing bars was less than 15% for the same reinforcement ratio. The precast FDDPs showed very similar results to those of the controlled slab reinforced with GFRP bars. The RC slab reinforced by steel reinforcing bars failed in the flexural mode, while the slab reinforced by GFRP bars failed in flexural-shear one.

A novel computer vision and point cloud-based approach for accurate structural analysis of a tall irregular timber structure

Wood material has been widely used in critical heritage structures such as pagodas, totem poles, and large-scale sculptures. Conducting rigorous structural analysis is crucial to protect these structures in high-seismic regions. Typically, these types of structures are modeled using an equivalent finite element (FE) model which used simple cylinder with a constant cross section equal to the average of the top and bottom cross section. However, simplified equivalent FE models may not accurately consider the irregularities and complexities of these structures. In this paper, advanced computer vision and point cloud techniques were adopted to accurately and rapidly construct a FE model of a 30-meter irregular timber sculpture. This was achieved using video scans, computer vision-aided 3D reconstruction, point cloud processing, and mesh to solid element conversion. The refined FE model was used to conduct capacity check, mesh sensitivity study, pushover analysis, and response spectrum analysis. The results of the refined FE model were compared to an equivalent FE model. The results show: 1) the proposed numerical modeling methodology for structural analysis can efficiently and accurately measure the dimension of the irregular sculpture up to 98.2 % accuracy; 2) the lateral stiffnesses of the 30-meter irregular sculpture vary significantly (up to 42.6 %) from one direction to the other; 3) the equivalent FE model overestimated the shear and moment capacities by 20.6 % and 13.2 %, respectively; 4) on average, the equivalent FE model overestimated the shear and moment demands by 8.9 % and 5.5 %, respectively. Overall, the proposed application has demonstrated a fast, economical and accurate method to conduct seismic evaluation and design for irregular structures.

Numerical modeling of the transfer length of 17.8 mm (0.7 in) diameter prestressing strands in pretensioned members

The bond between concrete and reinforcing steel bars in reinforced concrete structures is crucial. Prestressing strands with a diameter of 17.8 mm (0.7 in) transfer higher compression per unit area than smaller strands, improving moment capacity and shear strength and extending the girder span. However, limited research on the bond performance of these 17.8 mm diameter prestressing strands has restricted their widespread use despite their advantages. This study presents a methodology to determine the transfer length of pretensioned members numerically. The influence of pretension force and bond strength on a 17.8 mm diameter strand was assessed through the validation of a finite element model using experimental results from a standardized pretensioned pull-out test. Analytical calculations using different code formulas were also conducted, encompassing strands of varying diameters. Our finite element analysis suggests that a 50.8 mm spacing between adjacent 17.8 mm diameter strands is applicable, ensuring there is no stress overlap in the transfer zones, which can lead to concrete cracking and reduced structural integrity. Existing code formulas, such as ACI 318–19 and AASHTO LRFD 9th edition, require longer transfer lengths when compared with the numerical results. The fib MC 2010 and EC2 formulas offer closer results to numerical results of smaller diameter strands but underestimate the transfer length for the 17.8 mm diameter strand. Therefore, improvements to code formulations may be necessary for more accurate transfer length predictions for this specific strand size.

The Influences of Selected Factors on Bending Moment Capacity of Case Furniture Joints

This study experimentally investigated the effects of selected factors on the bending moment capacity (BMC) of case furniture joints. The main aim was to explore mixed applications of wood-based materials and fasteners in manufacturing case furniture to reduce material costs. The study examined the effects of the face member material—particle board (PB), plywood (PL), and block board (BB)—edge member material (PB, PL, and BB), and joint shape (T-shape and L-shape) on BMC. Additionally, the study evaluated the effects of joint type (two eccentrics (TE), two dowels (TD), and one eccentric and one dowel (ED)), and material type (PB, PL, and BB) on BMC for L-shaped joints. The results showed that joint shape and face member material significantly affected the BMC of case furniture joint. The BMCs of T-shaped joints were significantly greater than those of L-shaped joints, regardless of the material of the face and edge members, except when the face member was made of PL. For L-shaped joints with PL face members, the BMCs were significantly higher compared to others. Joints constructed with TE exhibited significantly higher BMC compared to ED and TD for the same material type. For PB, TE joints exhibited an increase of approximately 3.0 Nm and 2.0 Nm compared to TD and ED, respectively. For PL, TE showed an increase of 9.1 Nm and 4.1 Nm compared to ED and TD, respectively. For BB, the increases were 7.0 Nm and 6.6 Nm compared to ED and TD. The BMC of joints made with PL and constructed with TE and ED was significantly greater than those of BB, followed by PB. However, for joints assembled with TD, there was no significant difference among the three materials. The ratios of BMC for joints constructed with ED compared to the half-sum of TE and TD were 0.73, 1.04, and 0.79 for PB, PL, and BB, respectively. These results suggest that the face member material predominantly influences the BMC of case furniture joints, indicating the potential to reduce costs by combining different materials and joint types.

Moment Curvature and P-M Interaction Analysis of Steel and GFRP Reinforced Concrete Column

This research explores the use of Glass Fiber Reinforced Polymer (GFRP) bars and GFRP circular sections as longitudinal reinforcement in Reinforced Concrete (RC) columns, specifically to mitigate corrosion issues in harsh coastal environments. Twelve concrete specimens were prepared and tested under various loading conditions to evaluate the performance of GFRP as a substitute for conventional steel reinforcement. The experimental findings indicated that GFRP-RC columns displayed slightly lower axial load and bending moment capacities compared to steel-RC columns, though the ductility of both types was found to be similar. The study also highlights the significance of considering the role of GFRP bars in compression, supported by experimental results. This research offers valuable insights into the behavior and performance of both steel and GFRP-reinforced concrete columns, particularly in environments vulnerable to corrosion, with assessments conducted at 28 and 60-day intervals. A comparison of the outcomes from these timeframes reveals the effectiveness of GFRP as a reinforcement option in corrosive conditions

Analysis of Strengthening Beam Structure Case Study on Food Court Building of Ruang Terbuka Hijau (RTH) Project at Alun-Alun Kota Kediri

The Green Open Space (RTH) construction in Kediri City includes a food court building utilizing reinforced concrete structures. During construction, cracking issues occurred in several beam structures due to the inability to bear the design loads effectively, necessitating a strengthening approach. This study aims to develop and evaluate a strengthening method for cracked beam structures by employing concrete jacketing. The specific objective is to improve the structural integrity and load-bearing capacity of these beams to ensure the durability and safety of the building. A concrete jacketing technique was used to reinforce the cracked beams, utilizing K-300 ready-mix concrete and additional reinforcing steel. The study involved structural analysis to assess the load-bearing capacity before and after jacketing, and on-site evaluation was conducted to monitor the method's effectiveness. The findings indicate that the jacketing method significantly increased the beams' bending moment capacity and overall structural strength, successfully addressing the cracks and enhancing the beams' ability to bear the intended loads. The reinforced beams showed improved load distribution and structural resilience performance. Concrete jacketing proved to be an effective method for strengthening the cracked beam structures in the Green Open Space project. The study provides valuable insights for similar future construction projects, suggesting that concrete jacketing can be a reliable reinforcement technique to enhance the durability and safety of building structures.

Moment capacity of cold-formed steel channel beams with edge-stiffened and unstiffened elongated web holes

Cold-formed steel channel beams (CFSCB) often incorporate web holes to accommodate building services, but this reduces their moment capacity due to decreased web area. Recent studies have shown that a new type of edge-stiffened web holes can enhance moment capacity, especially for circular ones, and can now be extended to elongated web holes. However, there hasn't been research on the moment capacity of such CFSCB with elongated web holes. This paper uses finite element analysis (FEA) to examine the moment capacity and flexural behaviour of such beams with both elongated edge-stiffened web holes (EEH) and elongated unstiffened web holes (EUH). After validating the FEA models against experimental results available in the literature, a comprehensive parametric study involving 2160 FEA models was conducted. Results showed that CFSCB with EEH exhibited, on average, a 9 % increase in moment capacity compared to those with EUH. Additionally, the parametric results were compared with the design capacities calculated from existing standards for CFSCB with unstiffened web holes. It was found that the current design equations for CFSCB with EUH were overly conservative by 9 % and 66 %, on average, for distortional or local buckling failure and lateral-torsional buckling failure, respectively. Consequently, modified Direct Strength Method (DSM) design equations were proposed to calculate the moment capacity of CFSCB with both EEH and EUH. Finally, a reliability analysis was conducted to assess the accuracy of the proposed design equations.